An electric current measuring device has been proposed which has a conductor array composed of conductors arranged adjacent to each other but can accurately detect a current flowing through one of the conductors (see, e.g., Patent Literature 1 below).
The electric current measuring device described in Patent Literature 1 below is provided with a readout unit for reading output signals from four magnetic sensors arranged to sandwich each of the three parallel conductors of the conductor array, and a computing unit for calculating currents respectively flowing through the conductors based on the output signals read by the readout unit as well as a correction factor representing an effect of a predetermined magnetic field on the output signal from each magnetic sensor. The correction factor used for computing in the computing unit is pre-calculated by passing an electric current through only one conductor without passing through the other conductors, and is recorded.